After some further troubleshooting, I think found the bug... and it is an odd one.
If you set the RadDatePicker "SelectedDate" to a date within the current month, and then use the calendar popup to pick another date within the same month
, then the calendar does a full postback.
This causes the problem for me right now:
<telerik:RadDatePicker ID="RadDatePicker1" runat="server" SelectedDate="2008-10-01">
This does not:
<telerik:RadDatePicker ID="RadDatePicker1" runat="server" SelectedDate="2008-09-01">
I was able to further comfirm this involves the current month by changing the date on my computer clock to September, and the problem went away for SelectedDates in October, but returned if I set the SelectedDate to September.
I hope this helps. I have spent waaaay to much time on this and I am going to bed now. Let me know what you figure out.